Flexure-sensitive electromechanical transducer device



H. c. PAGE 2,62

FLEXURE-SENSITIVE ELECTROMECHANICAL TRANSDUCER DEVICE Jan.

Filed Dec. 28, 1948 FIG-2 Fl .l

SOURCE FIG. 5

JNVENTOR. HARRY C. PAGE ATTO R N EY Patented Jan. 6, 1953 UNITED STATESF PATENT OFFICE v FLEXURE:SENSITIVE ELECTROMECHANI- .ICAIL TBANSDUCE VEV C HarryCQP-age';Cleveland Heights; ohio assignor to The Brush.jDe.velopmentf Company, Cleveland, Ohio,; a corporation of, OhioApplication December 28, 1948, Serial .No. 67,741

(Cl;i 3'10 -8.5)

. 11 Claims. 1

This invention relates to a transducerdevice -electromechanicallysensitive-to flexure of an electromechanically responsive element of thedevice. More particularly, this inventionrelates to a bending-sensitiveor twisting-sensitive electromechanical transducer device in which suchflex- --ure is associated-with mechanical reaction between portions ofthe device containing material having electromechanical propertiessuch-that theindividual-portions tend to deform 'to differenit extentsduring-transducing from electrostatic-fieldenerg-y to mechanical energy.

:Inan application for Letters Patent ofthe -United States, Ser. No.67645, filed concurrently herewith in the-name of Hans- G. 'Baerwald'andassigned to thesamev assignee as the present invention, there isdisclosedand claimed-,inter alia,

- a iiexure-sensitive transducer device comprising a substantiallyhomogeneous body having a-substantial variation with location throughthebody of local electromechanical transducing properties. Oneportion ofthe body is conditionedby the applicationzof aunidirectionalelectric-potential to provide a 1 substantial--transducingresponse characteristic. In accordance with one arrangementdisclosed and claimed-in-the aforementioned application; thehomogeneousbody- -is madeup of permanently polarizable polycrystalline dielectricmaterial; "such as -barium titanate 7 "material,- which has beenconditioned by"-p'olari-.

zation with a-unidirectional-potential but a portion of which has beenat least partially depolarized by localized heating. The depolarizedportionexhibits practically no electromechanical response. Thisportion'may'occupy, say,,about half of the thickness "of a plate-shaped'or barshaped body. When the body "is subjected to, an incrementalelectric potential, the portion which remains polarizedtends to expandor contract.

- Mechanicalreaction of this electromechanic'ally. responsive portionwith the relatively unresponsive half of the body produces a flexure,specifically, a bending of lines extending lengthwise in the body, asupon the application of asignal potential across the bar.Conversely,subjecting the bar-to a bending displacement results in theappearance of a signal potential across the bar.

The'transducer device just described is very simple structurally andexhibits several advantages over the composite bender devices of'theprior art, which comprise two or more electroded plates or bars cementedtogether along major surfaces thereof. Nevertheless, a transducer deviceutilizing-such a homogeneous polycrystalline body requirescareful-treatmentto produce-difl "-ferent electromechanicaltransducing-response --characteristics'in-diiierent portions of thebody.

' Whenthe variation of the local electromechanical-transducingproperties within the body is ---achieved by electrostaticprepolarization and subsequent localized heating, only arepetition ofthis type of carefultreatment, utilizing special equipment, -canreinstate the device to a--useful condition-if the polarizationsubsequently should -be disturbed, for example by inadvertentheating -orlay-the application-of anunusuallyhighzsig- .nal potential-to the body.

-Accordingly,"it is an object of-the present invention to provide a newand-improved trans- ''ducer device electromechanically sensitive --to-:flexure which substantially avoidssome-orall -of the limitations anddisadvantages of devices hitherto proposed.

It is another object of the invention to provide a new :and improvedtransducer device electro- --mechanically sensitive-to flexure and ofsimpler construction .thancomposite bender and twister devices.

It 'isa further-vobjectof the invention to provide: a newiandzimprovedflexureesensitivetrans- ",ducer-device which-may be made to exhibit: a;-=reasonably;..'.high efliciencysofa.transducingafter ':,.2;'Sim131e.electrical treatment.

' It,is a still further'object cr me-invention to awprovide a novel,inexpensive, and. easily: manuzfactured fiexurensensitive transducerdevice.

accordance-With the invention, z t-transducer xdevice-electromechani-cally sensitive--toiiexure comprises. abodysubstantially free of structural discontinuities, having one substantialportionof a dielectric material which is conditioned bythe applicationof a unidirectional electric potential to provide 'a substantialtransducing-response characteristic as between mechanical signal energyand electrostatic-field signal energy and having another substantialportion of dielectric also comprises means including electrodes adja--material of diiierent composition which upon the "application'ofsaidunidirecti'onal potentialhas a transducing-response characteristica's'between the aforementioned signal energies substantially differentfrom the first-mentioned transducingresponse characteristic. Thetransducer device cent to the body for translating currents associatedwith the electrostatic-fieldsignal energy transduced in the body, andmechanical means for translating the motion associated with the =Jiexureduring 'transducing, this flexure being associated with mechanicalreaction between the -one portion of the body having the aforesaid sub-3 stantial transducing-response characteristic and the other portion ofthe body. As will appear hereinbelow, the last-mentioned portion of thetransducer body, which is of different composition from that of, and hasa different transducing-response characteristic from that of, thefirst-mentioned portion, may have a substantially zero-valuedtransducing-response characteristic and thus may exhibit no appreciableelectromechanical response except by mechanical reaction with thefirst-mentioned responsive portion.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawing, and itsscope will be pointed out in the appended claims.

In the drawing, Figs. 1 and 2 are front and side elevations respectivelyof an electroded body useful in devices embodying the present invention;Fig. 3 is an enlarged sectional plan view of this body taken in thedirection indicated 3, 3 on Fig. 2; Fig. 4 is a representative roughplot of the variation of the transducing properties of the bodyillustrated in section in Fig. 3 as a function of the thickness of thebody as viewed in Fig. 3; and Fig. 5 is a perspective view of atransducer device in accordance with the present invention, this devicecomprising the body illustrated in Figs. 1-3 and being shown inassociation with apparatus, illustrated schematically, for use in apreliminary electrical conditioning of that body.

Referring now to Figs. 1 and 2 of the drawing, there is illustrated athin body 2| substantially free of structural discontinuities, havingone substantial portion, more specifically a thickness portionunderlying and near the right hand major surface of the body, of adielectric material, and having another substantial portion, morespecifically a thickness portion underlying and near the left hand majorsurface, of a material of different composition. The body 2| may bedesignated as noncomposite, since it is not made up of two or morestructurally distinct parts. A composite structure, on the other hand,is one made up of two or more distinct parts or elements with apronounced interface therebetween. From a mechanical point of view thebody 2| is substantially free of structural discontinuities, although itis recognized that the microstructure of the body may involve numerouscrystalline grains having numerous interfaces but nevertheless formingessentially one structure as regards bending or twisting forces appliedto the body within the elastic limits. On the other hand, it is clearthat the composite elements of the prior art, constructed by cementingtogether two or more plates, have macroscopic interfaces. Theseinterfaces constitute structural discontinuities, in which, due at leastin part to imperfect adhesive properties of the cement used and to thedifferent shear moduli of elasticity of the materials in the regions ofthe interfaces and elsewhere in the elements, a substantial fraction ofthe mechanical energy available during transducing may be lost.

Generally speaking, a difference in the composition of the material intwo portions of the noncomposite body 2| may be realized in either oftwo ways. In one, the variation in composition through the body is agradual one. In the other, materials of substantially differentcomposition are present in neighboring portions of the body, but themolecular or crystal grain structure of the materials is so similar thatthe structural properties, determined at least to a large extent by thecohesive properties of the constituent materials and by their moduli ofelasticity, are substantially unbroken throughout the body. If one ofthe conditions just mentioned is not met, an interface usually appearswithin the body and the noncomposite character of the body is destroyed.However, it should be understood that local imperfections of a small andscattered nature may appear, for example in the regions of greatestvariation of the composition of the material, without destroying theessentially noncomposite nature of the body.

Electrodes 22 and 23 are aflixed to the body 2| in opposed positionsadjacent respectively to the left hand and right hand major surfaces ofthe body, as viewed in Figs. 2 and 3. As illustrated, unelectrodedmargins are provided at the top and bottom of the body to facilitatemechanical connections to the body. The electrodes are shown withexaggerated thickness for ease of illustration. They may be made, forexample, of conductive metal foil or of suitably bonded graphiticparticles.

In the cross-sectional plan View of Fig. 3, the body 2| appears as aunitary member with the central plane of its thickness indicated by thecenter line 24. The body 2| has the shape of a plate or bar of smallthickness compared with the other dimensions thereof. The one thicknessportion of the body underlying the electrode 23 and disposed generallyparallel to the major surfaces of the body is of a dielectric material,preferably a polycrystalline barium titanate material, which isconditioned by the application of a unidirectional electric potential toprovide a substantial transducing-response characteristic as betweenmechanical signal energy and electrostatic-field signal energy. Theother thickness portion of the body, underlying the electrode 22, isdisposed generally parallel to and laterally of the aforesaid oneportion and is of a dielectric material, preferably a polycrystallinedielectric material such as a modified barium titanate containingstrontium titanate, which upon the application of the unidirectionalpotential as mentioned above has a transducingresponse characteristic asbetween the mechanical and electrostatic-field signal energiessubstantially different from the first-mentioned transducing-responsecharacteristic of the one portion.

It should be noted here that the effective transducing response of a,portion of the body 2| may be determined in part by the distribution inthe thickness direction of the body of the signal potentials,corresponding to the electrostatic-field signal energy in the body,which appear between the opposed electrodes 22 and 23. As a result ofthe differences in the composition of the materials making up thevarious portions of the body, this distribution may not be the samethroughout the thickness of the body; in other words, the field strengthmay be different in different thickness portions of the body.Accordingly, for the purposes of this specification and the appendedclaims, it is convenient to define a transducing-response characteristicas the relationship between incremental mechanical energy per unitvolume of the portion of the body under consideration and an incrementalpotential difference across the entire thickness of the body, theincremental potential difference being associated with an incrementalelectrostatic field energy per unit volume. It isassumedgrasz'ordinarily. is .the case,- that polarizing. andisignal'.electricrfi'eldsz arev applied in. the? thicknesszdirection of the body,but .'fields'.ma'yib e -ap'-- pliedx'across a larger dimension;

In: the manufacturev of bodies. of thetype de-"- scribedfrompolycrystalline titanate materials; portions ofv the body maybeshapedcby methods. known generallyin theceramic arts. Thus a thin sheet.of. a dielectric material containing; primarily raw "barium.titanate-:may be formed by anyconventional method. After eventualceramic firing, a sheet of suoha material-mayibacon dition'e'd. toprovide' the desired response by. the application, whenever convenientandfoi' a pre determined period of time. of the order of a minute; of 'aunidirectional potential; The fired; material is susceptible to.remanent electrical. polarizatiom. which. persists. after: removal. of;the: unidirectional. polarizing. potential. Wherrrso polarized, this.material exhibits a .trans-ducing 're sponse characteristic which"notonly is of high: magnitude but also is substantially lineariover areasonable amplituderange; This largelinear response probably dependsboth on the:ipola1'"iza tionzof the dielectric material. by theunidirectional voltage applied thereto andon the. propertiesofthematerial before'polariz-ation. Another thin sheet of a dielectricmaterial containing primarilya raw barium-strontiumtitanate may beformed.v in like manner. The two fiatsheets of unfired material areplaced with a major sur.- face-of. each sheet in.mutu-al contact and.subjected to: a ceramic-firing. operation inwhich the interface betweenthe two sheets. is eliminated as far as structural. properties areconcerned by the incipient sintering' or vitrifying' actionwhichoccurs-during ceramic firing. After polarization in a manner describedhereinbelow, the resulting noncomposite body includes correspondingportions with substantial electromechanical transducing properties inthe portion containing primarily barium titanate and substantiallyweaker transducing properties in the other portion. However, in View ofthe care which must'be taken to insure substantial elimination of theinterface during firing, it is preferable to form asingle body of rawbarium'titanate and treat this body. chemically" to modify thecomposition of the barium titanatematerial in'one'nortfon ofthe' bodyiThus, the body may be modified'n'ear one major" face only by controlledamounts of a" material capable of reacting'with, orformin'g' a solidsolution with, the barium titanate to 'form' in-a portion of the body amaterial which after ceramic'firing is not susceptible to appreciableremanent'electrical polarization upon the ap-- pli'cation for apredetermined period of the unidirectional polarizing potential, orwhich at least' i's su'sceptible to remanent electrical polarization ofonly a lower order of magnitude than the remanent polarization of theuntreated barium titanate'material in the remainder of the body atordinary temperatures of use; The portion of the'body so treated mayexhibit no appreciable transducing-response characteristic, at'least inthe absence of a continuously applied unidirectional potential of highintensity. A material which might be used for this purpose is strontiumoxide, which is best used in the form of strontium titanate. Thetreatment may be carried out duringthe ceramic-firing operation, thematerial being applied to the side of the body being treatedxin:.finely. powdered form along with small amounts of a suitableflux; Duringthe firing:

the appliedimaterial: penetrates to a-;'.depth se tion of. the: bariumtitanate: material. canbe achieved, with? penetration. of. lessmaterial: into the titanazte body thanis the. case with. the strontium.-oxide material. Thus... modification of portions of the barium titanatematerialby incorporation therein of severalpercent by Weight of stannicoxidegreatly decreases the abilityof that portion of the material toexhibit transducingI-response characteristics when the firedbody isconditioned. by the applicationof a unidirec tional polarizingpotential. Whether. the m odie f-ying material. contains strontiumortin, smaller-' amounts of: modifying material may suifice: if, duringor following a temporary application of a polarizing. field, thetemperature of the body'is raised moderately to: remove remanent'polarization in the portion .o'f the-body whose composition .has' beenmodified asdescribed above.- It the temperature 'remains below" about1109' or 1'20 "C.,- the unmodified polarized barium titanate materialretains all or most of its remanent polar ization;

The noncomposite electromechanically sensi tive body 2|: also maybeformed by dipping a backing structure successively into aqueousdispersions of'ba'rium titanate and barium strontium titanate-to formcontiguous layers of thetwo' materials. This double-dipping process isdis-- closed and claimed in an application for Letters Patent of' theUnited States, Serial No. 67,695} filed concurrently herewith in the"name of Charles Gravley' and assigned to the same assignee asthe'present' invention; which issued onSeptember 25, 1951, as PatentNo;2,569,163! The body formed by this double-dipping opera tion then issubjected to ceramic-firing tem-- p'eraturesto establish a ceramicbond'betw'een the two layers which is substantially asstrong as thebonds within the individual layers and of substantially similar elasticproperties.

A plate-like body substantially free of structural discontinuities,formed by one of the meth-- ods suggested hereinabove, has'portions ofdifferent compositions differing substantiallyin their electromechanicaltransducing properties. At least the portions of this body which haverelatively high values of the local .el'ectro-- mechanical transducingproperties are'of adielectr-ic material, and in the examples mentionedhereinabove all portions of the bodyare of dielectric materials;Transducer bodies freeof. structural discontinuities and containing oneportion of a dielectric material and anotherportion of a conductivematerial are described and claimed in the aforementioned copendingapplication of Hans G. Baerwald. Often it is: convenient to form theportions of difierent compositions so that these portions have equalthicknesses. Then one portion lies generally to one side of thecenterline 24, Fig. 3, while therother" portion lies generally to theother side. In the region of the central plane the composition maychange more or less abruptly in the thickness direction, but without anyabrupt change in the structural properties of the material. However, itmay be desirable to make one portion considerably thicker than theother. For example, the portion having a transducing-responsecharacteristic of greater value may be thinner than the relativelyunresponsive portion. In such a case a chemical treatment for modifyingthe composition of the body near one side thereof might becomeimpractical, and it is recommended that the body be formed by the methodof the aforementioned copending Gravley application. Some of theconsiderations which determine the optimum relative thicknesses of thetwo portions of the body are discussed in the aforementioned copendingBaerwald application.

When the two layers of the body 2| have approximately equal thicknessesbut have different transducing-response characteristics uponconditioning by a polarizing potential, the transducing properties ofthe body may be represented in a rough manner by the plot of Fig. 4.This plot is aligned vertically below the transverse sectional view ofFig. 3 so that the thickness coordinate of the plot coincides with thethickness direction in the body as viewed in Fig. 3. The plot of Fig. 4may represent roughly the variation of the transducing propertiesthrough the thickness direction when the left hand portion of the bodyis a barium-strontium titanate material and the right hand portion ispolarized barium titanate material. In this case only the right handportion has substantial transducing-response characteristics, and thetransducing properties of the regions of the body near the left handmajor surface have zero values. In this connection it appears from theabove that the different polarization of the left hand portionadvantageously is a polarization of a lower order of magnitude than thepolarization of the right hand portion, with a correspondingtransducing-response characteristic of a lower order of magnitude thanthat of the right hand portion. In the case where the material of theleft-hand portion has a lower or residual, but substantial, localresponse, it will appear that a transducing property represented alongthe vertical coordinate in the plot of Fig. 4 would have a zero valuebelow the plotted curve, as at A0. As a matter of fact, if the left handportion is a barium-strontium titanate of the 70:30 mole ratio mentionedhereinabove, when a preliminary polarizing field has been applied andremoved, the different polarization of the left hand portion actually iszero with a negligible transducing-response characteristic therein,since this material does not retain remanent polarization. In this caseit appears that the local transducing properties in the regions near theleft hand surface have zero value, as indicated at B in Fig. 4:. In bothcases the two portions of the body just underlying its two majorsurfaces are of materials providing the extremes of values oftransducing-response characteristics in the body, which is a conditionconducive to efficient bending response of the body during transducing.The mechanism of the bending response, involving mechanical reactionbetween portions of the body having different values of theelectromechanical transducing properties, will be explained in greaterdetail hereinbelow. Any of various local transducing properties-might beplotted to 8 obtain the curve of Fig. 4; The transducingresponsecharacteristic as defined hereinabove may be used. In this case, forexample, after polarization of the body 2| by the application of a highunidirectional voltage across the electrodes in the thickness direction,the mechanical effect of the electric signal field resulting from theapplication of unit voltage across the electrodes is plotted for smallvolume portions of the body. The mechanical eiTect may be expressed interms of the fractional or percentage distortion or strain in adirection lengthwise of the body, since this type of strain isassociated with the desired bending response.

A complete transducer device which is electromechanically sensitive tofiexure is illustrated in Fig. 5. The device includes the body 2| andits electrodes, electrical circuit terminals 25 and 26 connected to theelectrodes 22 and 23 respectively, a base 2'! in which the lower end ofthe body 2| is mounted securely, a yoke 28 secured to the top of thebody 2|, and a rod 29 projecting horizontally from the yoke 28 forproviding mechanical coupling to the device.

For use in the initial polarization of the body 2| a unidirectional highvoltage source 30 may be connected to the terminals 25 and 26, forexample through a double pole switch 35. This connection may be madebefore or after the complete transducer device represented in Fig. 5 isassembled, and the switch 35 may be closed for a short period of timetoprovide the transducing properties represented by the plot of Fig. 4.A polarizing potential approaching the breakdown voltage of the materialmay be used, although lower polarizing potentials often are entirelyadequate. The polarizing connections to the terminals 25 and 28 then maybe removed and used in polarizing other transducer bodies. However, ifthe body should lose its polarization for any reason, for example byinadvertent heating above C., the polarizing arrangement easily may beemployed again to restore the desired transducing properties.

In operation, the device of Fig. 5 may be used to transduce fromelectrical energy to mechanical energy or vice versa. In either case,suitable electrical and mechanical means, not shown, are connected tothe electrical-circuit terminals 25, 26 and to the mechanical-couplingrod 29, respectively, to serve as source means or utilization means forthe energy transduced, as the case may be. Accordingly, the devicecomprises means including the electrodes 22, 23 and the terminals 25, 26for translating currents associated with the electrostatic-field signalenergy transduced in the body. Furthermore, the yoke 28 and rod 29constitute mechanical means for translating the motion associated withthe flexure of the body 2| during transducing. Thus a bending flexure ofthe body is associated with mechanical reaction between the righthand'portion having the substantial transducing-response characteristicand the left hand portion of the body. Application of a signal potentialacros the terminals 25 and 26 causes the more responsive right handthickness portion to expand or contract, resulting in a net bendingmotion by mechanical reaction with the opposed thickness portion havingnegligible electromechanical response. The bending motion is translatedby longitudinal motion of the rod '29 in the direction of the doublearrow, Fig; 5. Conversely, moving the rod 29 longitudinally causes a.bending of lines extending vertically in the de- 9:5vice',rresulting.rinztheiappearancc'xofrasignalipow tentia'l acrossthewterminals. i

Under some. circumstances; t for; irexample :io'r. operationathighfltemperaturesoriwith high-elecs tric signalpotentials,it'imayzbez:desirable.to;main-' tain-the" unidirectional voltage source:of.'. Fig;Z.5 1 connected" to the transducer: body: during: operation.:1 With such continuous: polarization thesre-: sponse of :a barium:titanate V material; is: higher:v than-with remanent'ipolarization;. Theunrespon sive portion 'ofi the body thent-"advantageously is r aabarium-titanate containing :bariumi'zstannate, which may beintroduced-by treatment with. stannic i oxide: as mentioned: 7hereinab'oven The rel-:7 sponse of the modified titanate :is-muchile'ss:.than: that' of 1 the barium titanate; even underts a :con-:-'tinuously applied polarizing field.

It is advantageous that the ielectromechanically unresponsive portionofthe. body 2 lf,th'at1is;:ithei left' handportion asrepresentedin FigSI'Ban'di'- Y be of adielectric material :of -'a':composition .WhiCh'i'has-a higher dielectric constantzzthan that :ofz th material: 'of th'e:more responsivaporti'on.ate-pre determined operatingtemperatures; suchas item: peratu-res between" "and. 100 For example; a barium strontiumtitanate may' havesa dielectrici constant 3 or 4 times thatofbarium2titanate, whil "-barium titanate containing several iweightpercent- 0f stannic oxide may have-a dielectric constant 'about twicethat- 0f the unmodified barium 'tit'anate.- When theelectromechanicallyi unresponsive-portion-has a higher dielectric conT-stant, the-several portions of the -bodyi'acte as a.;vo1tage=divider-made up of series capacitances: An electric potentialappearing 8.Cl'0SS th'-e1ltlr body 'then'=-'is associated with"ahigher-" fie'ld' strength in the electrom'echanically responsiveportion, increasing the transducing efficiency.

While" there have' been described what-areat presentconsid'eredto be thepreferred emb'o'di ments-of'this invention, it willbeobviousto'thoseskilled in the-art that various changes and modifications-maybemadetherein without departing from "the'in'vention', and it is,therefore; aimed in the appended claims'to cover all-"such'changes' and'modifications as fall within the true spirit and scope of the invention.

Whatis claimed'is:

1; 'Ai' transducerdevice electromechanically sensitive =to fiexurecomprising:- a' body substantially' free of structural discontinuities.-having one substantial portion of a dielectric materi'alwvhich isconditioned by" the application of a unidirectional electric potentialto provide a substantial transducing-response characteristic as betweenmechanical signal energy andelectrostatic-field' signal' 'energy, andhaving another substantial portion -0f a'dielectric material ordifferentcomposition which u on said application of said unidirectionalpotential:hasa transducing-res-ponse characteristic as-betweensaidsi'gnal'energies sub stantiallydifierent from f said first mentioned1o: thereof, substantially free of structural discontinuities, havingone-substantial thickness portion disposed-generally parallel to themajor surfaces of said body and of a dielectric material which isconditioned by'the application of a unidirectional electric potential toprovide a substantial transducing-response characteristic as betweenmechanical signal energy and electrostatic-field signal energy, andhaving another substantial thickness portion disposed generally parallelto and laterally of said one portion and of a dielectric material ofdifierent composition which upon said application of said unidirectionalpotential has a transducing-response characteristic as between saidsignal energies substantially *diiierent' from said first-mentionedcharac-teristic;'means for translating currents associated with saidelectrostatic-field signal energy transduced in said body, includingelectrodes in opposed positions adjacent to said major surfaces of saidbody and between which signal potentials corresponding to saidelectrostaticfieldsignalenergy may appear; and mechanical means fortranslating the motion associated with said flexure during transducing,said flexure being associated with mechanical reaction between said oneportion having saidsubstantial transducing-response characteristic andsaid other portion of said body.

3. A transducer device electromechanically sensitive to flexurecomprising: a thin body substantially free of structuraldiscontinuities, having near'one of the major surfaces of said bodyone-' substantialportion of a dielectric material which is conditionedby the application of a unidirectional electric potential to provide asubstantial transducingerespon'se characteristic as between mechanicalsignal energy and electrostatic-field'signal'energy, and having-near theothermajor surface'of said body another substantialrportion of adielectric material of difierent composition which upon said applicationof said unidirectional potential is effective to provide'atransducing-response characteristic as between said'signalenergiessubstantially different from said first-mentioned characteristic, saidone and said otherportions being of materials providing-the extremes ofvalues of transducing-response characteristics in said body; means fortranslatingicurrents associated with saidelectrostatici-fieldi'energytransduced in said body, includingelectrodesin opposed positions adjacent to said-major'surfaces'of saidbody and between which signal potentials corresponding to saidelectrostatic fieldsignalenergy may appear; and mechanicalmeans fortranslating the motion associated with said fiexure during transducing,said r'lexure being associated with mechanicalreaction betweensaid oneportion having said substantialtransducing-response characteristic andother portions of said body.

4. A transducer device electromechanically sensitive to flexurecomprising: a body subs-tantiallY-ireeofstructural discontinuities,having one substantial portion of a polycrystalline titanate dielectricmaterial which is conditioned by the application of a unidirectionalelectric potential'to provide'a substantialtransducingresponsecharacteristic as between mechanical signal energyand electrostatic-field signal energy; and having another substantialportion of a dielectric-material of diiierent composition which uponsaid application of said unidirectional-potentialhasatransducing-response characteristicas between said signal energiessubstantially difierent from said first-mentioned characteristic; meansincluding electrodes adjacent to said body for translating currentsassociated with said electrostatic-field signal energy transduced insaid body; and mechanical means for translating the motion associatedwith said flexure during transducing, said fiexure being associated withmechanical reaction between said one portion having said substantialtransducingresponse characteristic and said other portion of said body.

5. A transducer device electromechanically sensitive to flexurecomprising: a body substantially free of structural discontinuities,having one substantial portion of a polycrystalline barium titanatematerial which is conditioned by the application of a unidirectionalelectric potential to provide a substantial transducingresponsecharacteristic as between mechanical signal energy andelectrostatic-field signal energy, and having another substantialportion of a polycrystalline dielectric material of differentcomposition which upon said application of said unidirectional potentialhas a transducingresponse characteristic as between said signal energiessubstantially different from said first-mentioned characteristic; meansincluding electrodes adjacent to said body for translating currentsassociated with said electrostatic-field signal energy transduced insaid body; and mechanical means for translating the motion associatedwith said fiexure during transducing, said flexure being associated withmechanical reaction between said one portion having said substantialtransducingresponse characteristic and said other portion of said body.

6. A transducer device electromechanically sensitive to fiexurecomprising: a body substantially free of structural discontinuities,having one substantial portion of a polycrystalline barium titanatematerial which is conditioned by the application of a unidirectionalelectric potential to provide a substantial transducing-responsecharacteristic as between mechanical signal energy andelectrostatic-field signal energy, and having another substantialportion of a polycrystalline titanate dielectric material of differentcomposition which upon said application of said unidirectional potentialhas a transducing-response characteristic as between said signalenergies substan tially different from said first-mentionedcharacteristic; means including electrodes adjacent to said body fortranslating currents associated with said electrostatic-field signalenergy transduced in said body; and mechanical means for translating themotion associated with said flexure during transducing, said flexurebeing associated with mechanical reaction between said one portionhaving said substantial transducing-response characteristic and saidother portion of said body.

'7. A transducer device electromechanically sensitive to fiexurecomprising: a body substantially free of structural discontinuities,having one substantial portion of a dielectric material which issusceptible to remanent electrical polarization to provide a substantialtransducing-response characteristic as between mechanical signal energyand electrostatic-field signa1 energy, and having another substantialportion of a dielectric material of a different composition which issusceptible to remanent electrical polarization of only a lower order ofmagnitude than said remanent polarization of said dielectric material ofsaid one portion to provide a transducing-response characteristic asbetween said signal energies lower in magnitude than saidfirst-mentioned characteristic; means including electrodes adjacent tosaid body for translating currents associated with saidelectrostatic-field signal energy transduced in said body; andmechanical means for translating the motion associated with said flexureduring transducing, said flexure being associated with mechanicalreaction between said one portion having said substantialtransducing-response characteristic and said other portion of said body.

8. A transducer device electromechanically sensitive to fiexurecomprising: a body substantially free of structural discontinuities,having one substantial portion of a dielectric material which isconditioned by the application of a unidirectional electric potential toprovide a substantial transducing-response characteristic as betweenmechanical signal energy and electrostatic-field signal energy, andhaving another substantial portion of a material of a differentcomposition which has a higher dielectric constant than that of thematerial of said one portion at predetermined operating temperatures andwhich upon said application of said unidirectional potential has atransducing-response characteristic as between said signal energies of alower order of magnitude than said first-mentioned characteristic; meansincluding electrodes adjacent to said body for translating currentsassociated with said electrostatic-field signal energy transduced insaid body; and mechanical means for translating the motion associatedwith said flexure during transducing, said flexure being associated withmechanical reaction between said one portion having said substantialtransducing-response characteristic and said other portion of said body.

9. A transducer device electromechanically sensitive to fiexurecomprising: a body substantially free of structural discontinuities,having one substantial portion of a dielectric material which issusceptible to remanent electrical polarization to provide a substantialtransducing-response characteristic as between mechanical signal energyand electrostatic-field signal energy, and having another substantialportion of a dielectric material of a different composition which has ahigher dielectric constant than that of the material of said one portionat predetermined operating temperatures and which is susceptible toremanent electrical polarization of only a lower order of magnitude thansaid remanent polarization of said dielectric material of said oneportion to provide a transducing-response characteristic as between saidsignal energies substantially lower in magnitude than saidfirst-mentioned characteristic; means including electrodes adjacent tosaid body for translating currents associated with saidelectrostatic-field signal energy transduced in said body; andmechanical means for translating the motion associated with said flexureduring transducing, said fleXure being associated with mechanicalreaction between said one portion having said substantialtransducing-response characteristic and said other portion of said body.

10. A transducer device electromechanically sensitive to flexurecomprising: a body substantially free of structural discontinuities,having one substantial portion of a dielectric material containingprimarily barium titanate which is susceptible to remanent electricalpolarization to provide a substantial transducing-responsecharacteristic as between mechanical signal energy andelectrostatic-field signal energy, and

having another substantial portion of a dielectric material containingprimarily a barium-strontium titanate riot susceptible to appreciableremanent electrical polarization to provide a transducing-responsecharacteristic as between said signal energies substantially lower inmagnitude than said first-mentioned characteristic; means includingelectrodes adjacent to said body for translating currents associatedwith said electrostatic-field signal energy transduced in said body; andmechanical means for translating the motion associated with said flexureduring transducing, said fiexure being associated with mechanicalreaction between said one portion having said substantialtransducing-response characteristic and said other portion of said body.

11. A transducer device electromechanically sensitive to fiexurecomprising: a body substantially free of structural discontinuities andhaving polycrystalline dielectric portions of different compositions,including one portion containing primarily barium titanate withsubstantial electromechanical transducing properties and another portioncontaining primarily a bariumstrontium titanate with substantiallyweaker electromechanical transducing properties and a higher dielectricconstant than that of the material of said one portion at predeterminedop erating temperatures; means including electrodes adjacent to saidbody for translating currents associated with electrostatic energytransduced in said body; and mechanical means for translating the motionassociated with said flexure during transducing, said fiexure beingassociated with mechanical reaction between said one portion having saidsubstantiial electromechanical transducing properties and said otherportion of said body.

HARRY C. PAGE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 355,149 Dolbear Dec. 28, 18861,803,274 ,Sawyer Apr. 28, 1931 2,338,242 Arndt Nov. 6, 1945 ,394,670Detrick Feb. 12, 1946 25 2,402,515 Wainer June 18, 1946

